Listeriosis: Rare but dangerous for the elderly, expectant mothers and immunocomprimised persons
The number of cases of foodborne disease caused by listeria is rising continuously in Germany and the EU. Against this background, the German Federal Institute for Risk Assessment (BfR) is issuing a reminder that listeriosis caused by the consumption of certain foods is very severe and can result in death. "Above all elderly people, expectant mothers and immunocomprimised persons are at risk of contracting listeriosis," says BfR President Professor Dr. Dr. Andreas Hensel. "That is why very special rules for the consumption of certain foods apply in particular to these groups of people, along with kitchen hygiene".
The BfR has compiled comprehensive consumption tips in its leaflet "Protection Against Food Infections with Listeria".
The annual number of listeriosis cases in Germany recorded by the Robert Koch Institute has significantly increased since 2009 (from 396 to 771 in 2017). Although the infection occurs comparatively rarely, it has special significance due to the severity of its progression. Seven percent of the cases reported in 2016 resulted in death. The number of cases of listeriosis in the European Union has also risen since 2009.
Consumers can become infected and take ill through the consumption of foods contaminated with the bacterium Listeria monocytogenes. Due to their wide distribution in the environment and low growth requirements, the bacteria can occur in a wide range of different foods. Raw foods of animal origin, as well as foods that have already been heated or preserved in other ways, can be contaminated with listeria, as can ready-to-eat dishes and plant-based foods, such as fruit, vegetables, herbs and salads.
As listeria doesn’t cause food spoilage, their occurrence cannot be recognised by the appearance or smell of the food. It should also be noted that listeria propagate during refrigeration and in vacuum packaging. This means that foods which have been stored for longer periods can have a high bacterial count of disease-causing listeria despite being kept in the fridge. Elderly people in particular tend to keep food for much longer periods, either because they only eat small quantities or don’t like to throw them away. By doing so, however, they run an increased risk of contracting listeriosis.
Listeria are killed off by heating, e.g. through boiling, frying, roasting or pasteurising.
Elderly people in particular, as well as immunocomprimised persons (usually caused by a severe underlying illness such as cancer or long-term intake of immunosuppressant drugs), expectant mothers and newborn babies have an increased risk of contracting listeriosis. Severe cases can result in life-threatening blood poisoning, encephalitis and/or meningitis. In pregnant women, who often show only flu-like symptoms such as fever, exhaustion and muscle pain if at all, the infection can transfer to the unborn child and result in premature birth or miscarriage Due to the severe symptoms, infected infants have an increased mortality risk and can suffer severe impairments.
In healthy people who do not belong to a risk group, the uptake of large quantities of listeria can lead to a severe, feverish but usually self-limiting gastrointestinal infection with diarrhoea and vomiting.
According to estimations made by EFSA, one third of cases of listeriosis are due to growth of Listeria monocytogenes in food prepared and stored at home in the refridgerator. For this reason, the BfR urgently recommends strict compliance with the rules of kitchen hygiene and preparation of foods listed in the leaflet "Protection Against Food Infections with Listeria".
Special recommendations apply to risk groups. Accordingly, elderly people, expectant mothers and immunocomprimised persons should ensure that perishable foods which are not to be heated prior to consumption are prepared with fresh ingredients under conditions that are as hygienic as possible, and consumed quickly thereafter. This applies in particular to freshly squeezed juices and smoothies, sandwiches and filled rolls, as well as bakery products with uncooked fillings (e.g. cream, pudding or fruit). Fresh fruit and vegetables, leaf lettuce and fresh herbs should also be consumed soon. Perishable pre-packaged foods (e.g. cheese or cold cuts and cooked meat products) should only be purchased in small quantities long before their best before date, sufficiently cooled and used up within two or three days. In addition to this, the BfR recommends that consumers fundamentally avoid the foods in which listeria are most commonly detected unless they have been heated to a core temperature of at least 70° C immediately prior to consumption. The BfR gives detailed consumption recommendations in its leaflet "Protection Against Food Infections with Listeria".
In collaboration with the BfR, the Federal Centre for Nutrition has also published an information leaflet on its homepage containing the most important recommendations for protecting against listeriosis during pregnancy.
The Robert Koch Institute provides information on listeriosis on its website (https://www.rki.de/EN/Home/homepage_node.html).
About the BfR
The German Federal Institute for Risk Assessment (BfR) is a scientifically independent institution within the portfolio of the Federal Ministry of Food and Agriculture (BMEL) in Germany. It advises the Federal Government and Federal Laender on questions of food, chemical and product safety. The BfR conducts its own research on topics that are closely linked to its assessment tasks.
This text version is a translation of the original German text which is the only legally binding version.